Overhead electric cables are usually carried by porcelain insulator which are maintained upright by an upstanding pin engaging an axial blind bore of the insulator body, the pin fixed to the cross-arm of a ground pole or tower. The insulator has a saddle like upper portion which receives and supports the electrical cable. The latter is attached to the insulator by the difficult operation of manually winding and twisting a small diameter tie wire around the electrical transmission cable and a waist portion at the base of the insulator saddle portion.
In international patent application publication NO WO 91/03061 dated 7 Mar. 1991 for an “insulator for overhead electric wires”, there is disclosed a clasp which facilitates attachment of an electrical conductor cable to the insulator.
This clasp includes a metallic clamp and an elastomeric wire gripping element carried inside the clamp for surrounding and being pressed against the wire for firmly retaining the latter against longitudinal slipping. The clamp itself is a metal piece forming a central top web, with a pair of lateral downwardly extending opposite arms, in turn provided with inturned lower flanges, each having an inner partly circular recess. The clamp arms flanges remain spaced from one another at all times.
Conventional insulators have a lower bell-shaped portion and a saddle portion. The saddle portion includes a transverse electric wire-receiving groove and jutting parts on each side of the groove. The external surface of each jutting part includes a side face portion, which is downwardly inwardly inclined and which smoothly merges with the top of the bell-shaped portion at a narrowest waist area between the top saddle portion and the lower bell-shaped portion. In their operative condition, the above-noted prior art clasp arm flanges engage frictionally beneath the two corresponding insulator jutting parts, slightly above said narrowest waist area of the insulator, and on opposite sides of the insulator. The clasp arm flanges do not engage with one another.
When using the above-noted prior art clasp on an insulator, it was found that the clamp could accidentally detach from the insulator under certain load-induced circumstances.
There may therefore still be a problem of reliability in the electrical cable interconnection between the clamp and the insulator.